Program distribution for trains



Examz July 1u, 1:16a.

Patented July 16, 1935 Y J "o'fDelaware My present invention relates to radio broadcast program distribution systems, and more par.- ticularly to program distribution systems especially adapted for trains. i f t z One ofthemain objects of my present invention is to provide a system which is capable of receiving and distributing radio broadcast or local programs, such as recordings,l or local microphone pick-up announcements, etc. ontrains. the transmission from car tocar being. accomplished by the use of `the conventional battery connections already available, insulation of the battery, generator and lighting circuit being accomplished by.

means of suitable arrangements of reactors and Capacitors, .f f

Another importantobject of the present in `vention is to provide a system for the-reception and distribution of radio 'broadcast programs on trains, wherein existing lighting circuits of the train are utilized for transmitting the radio broadcast energy between cars, reactances being added in the lighting circuits in such a manner as to constitute a transmission line network with .desired characteristics, such as, proper impedance, cut-oli frequency and the like. :v: g

Another object of this invention ls to provid a system for radio reception and distribution of radio programs on trains, which system utilizes existing battery connections between cars, has a radio program transmission line, reactances being associated with the existing connections in such a manner that cars of a 'train not equipped for radio may be handled in'regular manner without special attention as to the number of :cars and location in a train, it thereby being possible to couple a car not equipped :for radio between .Iadio equipped Cars. "zii .G'f'ffj i i Still other objects of the present invention are to improve generally the simplicity and eiciency of radio broadcast distribution systems for trains,

and to especially provide a system which is knot Aonly reliable in operation, but economically installed in a train, andhighly flexible in assembly .when making upatrain. .I

.t The novel features which I believe to be charf acteristic of my invention are set forth in particularity inthe appended claims, the invention itself, however, as to both its organization and lmethod of'operationwill best be understood by reference tothe following description taken in connection with the drawing in which I have indicated d'iagrammatically one circuit an'angement whereby vmy invention may be carried into effect.

In the accompanyingv drawing there is shown invdiagrammatic manner iajradio broadcastV pro- 1Q-; IPRoGRAM DlsrRrUTionFonrrnAnys-J' 'f f Altan. napkins, Merchaitiiifni.; j to Radio Corporation ot Amerca,a"icorpora tion Application May 10,.1952Qseriai naciones? it rclaim. (ci.

assigner gram distribution system primarily adapted for receiving and distributing radio broadcast pro# -g'ram's on4 trains. The laccompanying drawing only shows threecars of a train,it being understood that -tlie rectangular dotted f lines, represent independent cars of' 'a train. Thus,-"car A is designated jas the fMaster receiver car;'car B is designated as a Coupling car.-and car C is designated as'a Radio-equipped 'car. =1`hatrist say; car VAcontains the'receiving equipment for collecting 'a radio broadcast program, and changing the freqencyof the collected energy to an audioor intermediate frequency, 'and distributing such resulting detected lenergy to -ksuchl cars of the train L which are equipped for program reproduction; '17' "'Car B islde'signated as a coupling car in view '0f the 'fact vthatit merely serves to-transmit the energy to radio equipped cars, car'B itself not being desired, Afor one reason or another, to I'be equippedwith radio reproduction devices. It will lthus be appreciated at the outset that the present system is highly-exible since the master receiver car maybe situated at any point along'the train, and that'the non-radioequipped cars may be dis'- boxes .A, B and C, in v posed in the trainin any manner, since the so- 'i' 'The conductorsA I, represent the existing battery,- generator and lighting circuit conductors common to all'the cars in the train and running through all the cars of the train `in proper conduit- (not shown to' preserve simplicity of disclosure). l'l'he conductor Prepresents the negative side of the existing power circuit of the train, .while the conductor 2 represents the positive 'side of'the'fsaid circuit. The :lighting circuit L connected between theconducto'rs I; 2 of each car represents 'the conventional 32 volt light system of each car, the letter G designating the usual-32 volt storage battery connected in parallel with the light system L in each car between the con# ductors I and 2. i-if'f' ,vi-In shunt, -ln each car, with each battery G is connected thel customary generator H, a condenser-H being connected ,in shunt with each battery G in order toby-pass the commutator ripple and static interference of generator H, and also to minimize the effect of changes in lighting load and changes in battery resistance. :This condenser 'eifectivelyggrounds the low, potential' side of the network.1-'Ihe conventional representation ,K in series with each generator H designates the usual voltage regulation vdevlca, 'Ihe condenser tu ...M

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H is not a part of the existing circuit but a unit which is to-be added to effectively ground one side of the transmission network.

Having now described the essential features of the existing battery cable circuit of a train, the master receiver car equipment will be explained. This equipment preferably comprises a conventional superheterodyne receiver having the antenna terminal and its input connected in the usual manner to'an outside antenna, which antenna may be disposed on the roof of the master receiver car. The ground terminal of the receiver input may be grounded by connection to the grounded frame of the car, the latter preferably comprising the observation car and club car of a train, although it is to be clearly understood that the master receiver equipment may be disposed in any other car of a train.

The central receiver equipment is preferably a conventional superheterodyne receiver noti-employing a second detector and succeeding stages if intermediate frequency carrier is used, but if the entire audio range is to be transmitted, it is necessary to use the second detector and audio system of the receiver. However, if program reproduction is desired in the master receiver car, then the second detector and succeeding stages are to be employed in the masterreceiver car. Since the receiver employed in the master rceiver car is of a conventional type, the various circuits thereof have been conventionally represented, as a radio frequency amplifier 3, a local oscillator 4, a first detector 5, and an intermediate frequency amplier Assuming that program reproduction is desired in the receiver car A, a second detector 'I is coupled te the output of the intermediate Vfrequency amplifier, and -an audio frequency amplifier 8 is utilized to amplify the audio frequency output of the second detector 1 to the proper audio level desired for the operation of the ioudspeakers. l

It is to be understood that the amplifiers 2, .6 and 8, may comprise one or more stages of amplification. In order to maintain the gain of the amplifier 3 of the receiver at a substantially uniform level, a conventional type of automatic gain control circuit 9 is utilized between the second detector and the amplifier 3 to control the gain of radio frequency amplication. It is not-believed necessary to describe such a gain control circuit in detail, since the arrangement shown in the patent issued July 3, i928 to Friis No. 1,675,848 maybe utilized. l

`The circuits of the various components of the central receiver equipment are preferably energized from the 32 volt battery source G, through a power supply converter D which is connectedin shunt across the terminals of the battery G. 'The dotted lines I0 designate the conductors supplying energizing power from the converter D. `As stated heretofore, if program reproduction is des ired injthe master receiver car A, a second detector and audio frequency amplifier are connected to the output of the intermediate frequency amplifier 6. The audio output of the amplifier -8 is then distributed over a loudspeaker line II, and a headphone line l. The line II has coupled to it loudspeakers I3 located in such spaces of the car A which are public, while the i headphones I4 are usually situated where individual reception is desired.

VAThe audio frequency amplifier 8 should have sufiicient amplification and power output to meet the requirements of'one car, it being understood of course that the lines II and I2 are at different volume level since the head phones do not' require as great a power level as the loudspeakers. Furthermore, there may be coupled to the headphone line I2 so-called radio pillows I5 which comprise head phones disposed within an inflated pillow, or rubber padded pillow so that reception may be had while a person reclines. Such a radio pillow is disclosed by E. J. Quinby in his application Serial No. 412,044 filed December 6, 1929.

The output of the intermediate frequency amplifier 6 is, additionally, tapped by leads I6, II which connect the output of the amplifier- 6 across the conductors I, 2. In this way the amplified intermediate frequency energy of the central receiver may be distributed over the existing battery circuit conductors I, 2 to radio equipped cars in the train. 'I'he system as described in the drawing involves the transmission of modulated intermediate frequency which would be approximately 175 kilocycles if a standard broadcast receiver is used. Therefore itis only necessary that the network be designed to transmit a relatively narrow band, say 170 to 180 kilocycles, or 165 to kilocycles. More than one channel would require a correspondingly wider band. This is only necessary where the audio energy is being transmitted. In this case the second detector and audio amplifier of the broacast receiver is used to amplify the audio frmuency.

However, in order to insure proper transmission of such energy over the path comprising the conductors I, 2, the battery, generator, and lighting circuit must be properly insulated from the radio equipment, and there must be added reactances of proper constants to the path I, 2 such as to provide a transmission network of suitable impedance for the transmission of the central receiver output to the other cars of the train, and to additionally design the line network to give satisfactory transmission of the entire audio frequency range. This is accomplished by connecting in# ductive reactors 20, 2l in series in the conductive path 2, the common terminals of reactors 2li, 2l being connected to the positive terminal of the battery G.

A capacitor 22, of suitable magnitude, is additionally connected in the conductive path 2, and in shunt with both reactors 20 and 2 I. This addition of inductive and capacitive reactors is employed in each oi' the cars. Thus, the car B includes the series inductive reactors 20' and 2i' andl the shunt capacitor 22', while the car C includes the series inductive reactors 20 and 2I"`, and the shunt capacitor 22". It is to be clearly understood that the constants of the various inductive and condensive reactors used in each of the cars are such as to constitute a transmission line network, with desired characteristics, such as proper impedance, cuto frequency, and the like. The choice of constants depends upon the frequency range of the energy transmitted over the common path I, 2. Those skilled in the art will understand the manner of choosing such constants so as to constitute the path I, 2 a proper transmission network for audio modulated energy, and it is therefore not believed necessary to assign any particular values to such constants, except to point out that the L and C values of the line network should be designed to give satisfactory transmission of the desired frequency range, which may be a relatively narrow band to transmit a' modulated intermediate frequency carrier or a very wide band as would be necessary to transmit the audio :wand .'Additionally, the

output transformer of th receiver amplifiersv should be designed to match the impedance of the loaded transmission line l, 2. This latter feature is also well known to those skilled in the art, and need not be referred to in any further detail.

The constructional details of a typicalradio equipped car are now to be discussed, special reference being had to car C. In this car there is provided adetector for demodulatingtheintermediate frequency carrier energy transmitted over the network L12, the leads 30, 3| feeding the intermediate frequency energy into the second detector 32. Suitable coupling means is interposed between the transmission line and the grid of the detecton4 A selector circuit is alsol necessary where more than one channel is used. TheL audio frequency amplifier 33, of one or more stages,l is coupled to theroutput of the second detector, and its output is fed into a loudspeaker line 34 and a headphone line 35. 'Ihe headphone line 35 is provided with a desired number of headphones 36, or radio pillows 31, while the loudspeaker line 34 is provided with the desired number'of loudspeakers 38 for use in the public spaces of car C. A power supply converter 40 is connected across the battery G, and supplies the circuits of the receiver unit components 32 and 33 with suitable energy, as shown by the dotted lines 4|.

It will be observed that al1 radio equipped cars, such as car C, have the battery, lighting and generator circuits effectively insulated, as in the case of the master receiver car. Each radio equipped car is wired throughout to supply a requiredI number of speakers and headphones with the proper audio frequency energy, the lines 34 vand 35 being at different volume levels. When a car, such as car B, which is not equipped for radio reception is inserted between other radio equipped cars, it is preferable to add the reactors and capacitors so that the new car can be inserted in the regular manner. But for emergency connections, a jumper cable. 50 may be utilized, as shown ln dotted lines, to eliminate the regular car from the radio train line.

All equipment on crack, or special, trains may be equipped in this way so that cars of a train may be handled in the regular manner without special attention to the number of cars and location in a train. It will be noted that the battery load is distributed by the use of special amplifiers for each car. It is believed that the operation of the present invention will be clear from the aforegoing description and the accompanying drawing.

However, to briefly review such operation, it will be seen that the central receiver in the master receiver car is adjusted to select a particular radio broadcast program, the program being reproduced in the master receiver car A through the reproducers coupled to the amplifier 8. Simultaneously, the program is distributed to other radio equipped cars through the leads I B, Il, the program being distributed at intermediate frequency. The path comprising the conductors I, 2, which path additionally includes the inductive and con densive reactors in each car, transmits the intermediate frequency energy throughout the train, the condensers 22, 22' and 22" permitting the iiow of intermediate frequency energy around the lighting, generator and battery circuits of each car, and the path of inductive reactors in each car blocking the ow of intermediate frequency energy through the lighting, generator battery circuits of each car.- Y i Each coupling car B serves to transmit inter- Cross Reference mediate frequency energy to a radio equipped car;

and in the latter intermediate frequency energy is supplied 'to a second detector and an audio amplifier. It will be understood that the input circuit'of the second detector in a car such as C is tuned to the intermediate frequency employed,V

distribution of intermediate frequency` energy. For example, the output of the second detector could readily be distributed throughout the trans mission network to radio equipped cars; indeed in that case, it would be merely necessary-tol employ an audio frequency amplifier in each car C. Furthermore, the invention is not limited to the use of a superheterodyne receiver in the mas-v ter receiver car A,`sihce a tuned radio frequency type of receiver can be employed in a car A, 'and the detector output be distributed to audio 'fre-A quency amplifiers in the various cars. The essen-F4 tial feature of the invention resides inthe utiliza-5 tion of the existing common battery circuit cable of the train, appropriate reactors being employed in each car, as a transmission network for program modulated energy to be reproduced in desired cars of the train.

Of course, the modulated energy distributed to the cars may be local announcements and recorded programs, as well as radio broadcast programs. The usual microphone or phonograph electric pick-up would then be used.

While I have indicated and described one arrangement for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organization shown and described, but that many modificationsmay be made without departing from the scope of my invention as set forth in the appended claims. Y Y

What I claim is: y

1. In combination with the common direct current lighting circuit and transmission line of a train of cars, a radio receiver including an intermediate frequency amplier in one car, means connecting the output of said amplifier to said transmission line, a second detector and an audio amplifier in a second car, means connecting the input of said detector to the opposite sides of the transmission line in said car, a direct current generator connected across the opposite sides of said line in said second car and two inductors connected in series in said line the positive terminal of said generator being connected to the common terminal of said inductors and a condenser connected across the outer' ends of said inductors,` said inductors and condenser being so designed as to make the transmission line within said second car a path of low impedance to energy of the intermediate frequency.

2. In combination with the direct cin'rent lighting circuit and transmission line of a train of cars, a radio receiver including an intermediate frequency amplifier in a iirst car, means connecting the output of said amplifier to said transmission line, a second detector and an audio amplifier in a. second car, means connecting the input of said detector to said transmission line, a direct current generator in each of said named cars having its terminals connected to the opposite sides of said transmission line, two reactors connected in series in said line in each of said cars, one terminal of said generator being connected to the common tras-fa terminal of said reactors and a condenser connected across the end terminals of each pair of reactors, said reactors and condensers being proportioned and arranged to make said line a path of low impedance to currents of said intermediate frequency.

3. In combination with. the direct current lighting circuit and transmission line of a train of cars, a radio receiver including an intermediate frequency amplifier in a first car, means connecting the output of said amplifier to said transmission line, a second detector having its input circuit pretuned to said intermediate frequency in a second car of said train, an audio ampliner and a sound reproducer coupled to the output circuit of said detector, connections between the input oircuit of said detector and the opposite sides of said transmission line, two coils connected in series in said line in said second car, a direct current generator having one terminal connected to the com mon terminal of said coils and its other terminal connected to the other side of said line, a storage battery connected in shunt across the terminals of said generator and a condenser having its opposite sides connected to the outer terminals of said coils, said coils and said condenser being designed to efficiently transmit said intermediate frequency energy to said second detector.

4. In combination with the direct lighting current transmission line of a train of cars, a radio broadcast receiver including an intermediate frequency amplifier disposed in one of said cars, a plurality of sound reproducers disposed in another of said cars, means for connecting said amplifier and reproducers to said transmission line including a second detector having its input circuit resonant to said intermediate frequency, at least two inductive reactances located on each car and connected in series with said transmission line and a condenser connecting the outer ends of said reactances, said reactances and condenser being designed to make the transmission line within each car a path of low impedance to the intermediate frequency energy and a source of direct current potential connected to the opposite sides of said transmission line in each car.

ALVA R. HOPKINS. 

